New details emerged today of Boris Berezovsky’s secret “begging letter” to Russian president Vladimir Putin in which he is said to have pleaded for “forgiveness” before his death.

It was claimed today that the oligarch wrote to Mr Putin this year offering to drop his accusations over the death of his friend Alexander Litvinenko if he were allowed to return to Russia.

A post-mortem examination was due this afternoon after the tycoon’s body was removed from his Ascot home last night. There have been reports that Mr Berezovksy, 67, was “very depressed” but other close associates expressed doubts he would have killed himself.

In the first direct quote from the alleged letter, Mr Berezovsky is said to have written from London: “I made a lot of mistakes. I understand it may be hard to forgive me, but I got tangled here and I am begging (you) to forgive me.” It was quoted on Russian TV show Iron Ladies and the source was said to have read the letter to Mr Putin.

Claims have been made in Russia that Mr Berezovsky was trying to negotiate a return home after years of exile. He is said to have raised the issue with a close political ally of Andrey Lugovoy, seen by the British as the main suspect in the polonium poisoning of Mr Litvinenko in London in 2006.

Mr Litvinenko’s inquest is due to take place in London this year and Russian Investigative Committee — the equivalent of the FBI — had been expected to argue that the oligarch could have been complicit in his death. Russian MP Lugovoy, a former FSB security service operative, denies any involvement and Russia has refused to extradite him.

Vladimir Zhirinovsky, a founding leader of the political party Lugovoy represents, has claimed he discussed Berezovsky’s potential return during a chance meeting this year. Mr Zhirinovsky said: “He promised to close down the Litvinenko case.”

Russian journalist Ilya Zhegulyov, who met the tycoon less than 24 hours before he was found dead in his locked bathroom on Saturday, said he had said there was “no point” to his life. He had lost a series of costly court battles against Roman Abramovich and his former partner Yelena Gorbunova.

However, Mr Litvinenko’s widow Marina said: “From my point of view it is not likely that he committed suicide.” Mr Berezovsky’s ex-wife, Galina, reportedly told friends a scarf was found next to his body. Nikolai Glushkov, who spoke to her, told the Guardian: “Boris was strangled. Either he did it himself or with the help of someone.”